(OT) virus reports sent back to me by PC users

[F. Mortes]

Dear friends,

I need a little help.

Over the last few months, I've been getting an awful lot of what 
appears to be messages created by virus detection systems on other 
people's computers, informing me that I've sent them a message 
containing a virus. Most such messages come from people I do not even 
know ... and sometimes include .exe attachments!

But in other cases these come from people I regularly deal with and, on 
one occasion, I've had a concerned call from a customer whose IT Dept. 
blame ME for "the repeated infection attempts" she has been suffering, 
allegedly by messages sent from my computer. Now, I very rarely send 
this customer e-mails and certainly not as often or when she claims she 
has got them ...

I know that there are no known viruses yet for Jaguar (except some 
trojan that can disguise itself as an .mp3 file?) and my Powebook (Ti 
550) is working like a charm, but ...

... could I be infecting other users and their PCs?

Is there anything I can do to stop receiving those annoying messages or 
to reassure my concerned customer?

Thank you in advance!

Francesc in Catalonia